Integration of a cogeneration unit into a kraft pulping process

Abstract

The integration of cogeneration with other measures that impact the power production capacity in a Canadian Kraft pulping mill is studied. Those measures are removal of pressure reduction valves, adjustment of the steam pressure level, biomass boiler capacity, and reduction in process energy demand. CADSIM Plus software is used to simulate the cogeneration plant. The dynamic behavior of the process during start-up and its effect on electricity generation are also considered. It is shown that by replacing the PRVs with turbines, 14.4 MW of power can be generated. Moreover, by implementing cogeneration units and process measures to recover 23% of internal energy, 44.5 MW of electricity can be generated in addition to shutting down the existing bunker oil boiler. Therefore, implementation of cogeneration in the pulp and paper industry is technically possible and it offers significant economic advantages. A cost analysis of the complete project gives a simple payback time of less than a year.